The present invention is generally related to packages for integrated circuits, and more specifically to a method and mount for high frequency integrated circuits in which the inductance of the path between the IC and ground is decreased to improve high frequency performance.
Many types of integrated circuits (ICs) are packaged in plastic by suspending the IC in the plastic and extending electrical leads to the IC through the plastic.
High frequency ICs desirably have an electrically conductive path between bonding pads on the IC surface and ground that desirably has low inductance and low electrical resistance. To this end, it is known to mount a bottom of an IC 10 on an electrically conductive metal paddle 12, such as shown in FIG. 1, or on an electrically conductive metal slug 14, such as shown in FIG. 2. Grounding wires 16 connect bonding pads 18 on a top of the IC 10 to the paddle 12 or slug 14. The paddle 12 or slug 14 and its accompanying IC 10 may be suspended in a protective package 20 (e.g., plastic) with a portion of the paddle or slug exposed for contacting ground (the electrical leads for the IC that extend through the package are not shown in FIGS. 1 and 2 in the interest of clarity).
As is known, the skin effect restricts the flow of high frequency current into the metal conductor to only a few microns. Therefore, increasing the surface area of an electrical conductor decreases inductance to high frequency currents. Thus, the electrically conductive path between a high frequency IC and ground desirably is short and has a large surface area.
Further, high power dissipation single-ended ICs need a path between the back of the IC and a heat sink that has a low thermal resistance.
Conventional electrical leads through a package to the IC have too much inductance in the path to ground for high frequency operation and too much thermal resistance for high power operation, and a separate low inductance, low thermal resistance path to ground and to a heat sink is desirably provided.
Accordingly, it is an object of the present invention to provide a novel mount and packaging method for improving the performance of a high frequency IC.
It is another object of the present invention to provide a novel method and mount for an IC in which the mount's surface area is more than that of prior art mounts so that the inductance in the path connecting the IC to ground is decreased.
It is yet another object of the present invention to provide a novel method and mount for an IC in which columns are provided at sides of an IC mount to increase the surface area of the mount, thereby decreasing inductance to high frequency currents in the path between the IC and ground.
It is still another object of the present invention to provide a novel method and mount for a high frequency IC in which an electrically and thermally conductive metal base for mounting the IC includes a plurality of trenches into sides of the base that extend from an upper to a lower surface thereof for increasing a surface area of the mount where each land between adjacent trenches is connected to a separate ground terminal on the IC to provide isolation between lands.
These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of the preferred embodiments.